The present invention relates to contrast inflow detection in fluoroscopic images, and more particularly, to detecting whether contrast medium is used in a sequence of fluoroscopic images and detecting at which frame in a sequence of fluoroscopic images the contrast inflow begins.
Computer-aided and image-guided interventions have become more important in recent years for advanced cardiovascular treatments. Medical images, such as 2D fluoroscopic (x-ray) images are widely used for pre-operative planning, intra-operative guidance, post-operative assessment. During an intervention, an angiography is often acquired in multiple phases of the procedure. An angiography is typically acquired by injecting a radio-opaque contrast agent into the blood vessels of a patient and then acquiring images using x-ray fluoroscopy. The contrast agent allows a physician to visualize the vessels and the blood flow in the fluoroscopic images.
Although it is often easy for a physician to tell when the contrast agent is present in fluoroscopic images, an automatic contrast inflow detection method is desirable for many computer-aided intervention procedures. Ideally, the overall intensity histograms over the temporal domain can be used to detect sharp changes of image intensity as potential candidates of the start of contrast inflow. However, this works poorly in practice since the moving diaphragm, which often appears in cardiac x-ray images, can easily mislead the contrast inflow detection. A main challenge of contrast inflow detection is due to the variability of the data, especially when the images are acquired in low dose radiation with a lot of noise.